Reduction method

ABSTRACT

A system and method for the direct reduction of iron by utilizing powdered hard grade, high melting point coal tar pitch that does not become soft and maintains its dry state at ambient temperatures in the formation of compact briquettes under high pressures and the reduction of such briquettes to metal.

United States Patent 1191 1111 3,918,956

Baum 1 Nov. 11, 1975 [5 REDUCTION METHOD 2.876.094 3/1959 Lusby 75/1112.911319 11/1959 M H b t 75136 [76] Inventor: Jesse 10419 K6150 Dnve-3.053.648 9/1962 st hinf 75/3 'W 85351 1351.459 11/1967 M1115 75/3 [22Filed: Jul. 3 1970 3374.085 3/1968 Stone 75/3 [2 [1 Appl' 54427 PrimaryE.t'ami11er-Hylz1nd Bizot R l t d U A li i Assistant E.\'uminerPeter D.Rosenberg [63] Cntinua1tion-in-palr1 of Ser. No. 591.997. Nov. 4 Agwm flByrne; Edward E.

1966. abandoned.

15:} us. 01. 4. 75/3; 75/4; 75/43; [57] ABSTRACT [5 H 1m. C2) 1/08. Cslb1/78. C7 w??? A system and method for the direct reduction of iron [58]Field of segrch h 75H by utilizing powdered hard grade. high meltingpoint d 37 coal tar pitch that does not become soft and maintains h 1its dry state at ambient temperatures in the formation [56] ReferencesCited of compact briquettes under high pressures and the UNITED STATESPATENTS reduction of such briquettes to metal 2.650.160 11/1953 Totzek/29 9 C|aim$- 17 Drawing Figures U.S. Patent Nov. 11, 1975 Sheet 1 #83,918,956

Wk. M32. 193. wmmwza 312'.

US. Patent Nov. 11, 1975 Sheet 2 0f 8 US Patent Nov. 11, 1975 Sheet 3of8 3,918,956

Sheet 5 of 8 manna.

Nov. 11, 1975 U8. Patent US. Patent Nov. 11, 1975 Sheet 6 of8 3,918,956

U.S. Patent Nov. 11, 1975 Sheet 7 of8 3,918,956

US. Patent Nov. 11,1975 Sheet 8 of8 3,918,956

FIG. 15

REDUCTION METHOD This application is a continuation-in-part of mycopending application Ser. No. 591,997, filed Nov. 4, 1966, and nowabandoned, which is based on my Philippine applications Ser. Nos. 6872,filed Nov. 18, 1965, 7330, filed May 16, 1966, 7385 filed June 7, 1966,and 7427, filed June 29, 1966, for which priority is claimed under 35USC 119 for the subject matter disclosed in said parent.

This invention relates to method for preparing briquettes of iron oreand or other oxide ores, furnace and component constructions and thedirection reduction of iron ore and or other oxide ores and apparatusfor reducing iron ore and other metallic oxide ores. More particularly,this invention relates to methods and apparatus for producing iron bydirect reduction of oxides or iron ores such as Fe,o,, (Hematite), Fe O(Magnetite), and FeO such as mill scale, and oxide ores of chromium,manganese, and copper. Specifically, this invention also relates to anovel method for preparing briquettes of such oxide ores, whichbriquettes may be subsequently reduced in a continuous process with themanufacture thereof or may be sold as articles of commerce.

Generally, the technology of the invention described herein is relatedto methods, apparatus, and techniques for producing a light porous ironcommonly known as sponge iron; however, as will appear hereinafter, thisinvention contemplates a directly reduced metal product which has verysignificant and unexpected characteristics which distinguish the productand the process from conventional sponge iron production.

The present invention relates to a shaft furnace, generally a verticalor slanted shaft, which is used to process a charge of iron ore and areductant such as coal or oil at a high temperature in the approximaterange of 1,900 P. to 2,200F. to produce iron. When 1 refer to iron, Imean the product obtained by removing the oxygen from various oxides ofiron ore to be processed such as Fe,o,,, Fe O and FeO such as millscale, the resultant product after processing being mainly high densityconcentrate iron.

One object of this present invention is to change or convert iron oredirectly to the metal without causing the ore to go through the moltenphase. The present invention requires much less heat energy than othermethods such as the blast furnace because it removes oxygen from the orewithout changing the physical characteristics of the ore. This makes forlower cost of production.

Another important objective of this invention is to provide a crucibletube having an inner liner of graphite and an outer liner of siliconcarbide.

In systems of the type involved herein it is known to use a coal tarpitch as a reductant binder. The reductant herein is of a type to matchthe particle size of the concentrated granular or powdered ferritematerial. The two are mixed together with a small amount of moisture ofapproximately 6 percent so they will hold together for briquetting. Astill further objective of this invention is to provide a mixture forforming briquettes where approximately 50 to 90 percent of same passesthrough a 325 mesh.

1n the invention described herein, vertical or slanted tubes areutilized to reduce the labor involved. An angle of recline of the tubesis utilized so that a briquette will move through the tube aided bygravity.

One of the important contributions of this invention is in the use ofhigh-frequency induction electricity for iron reduction purposes. Thereare two principal types of reduction methods described herein. One, theindirect method, uses a tubular retort or crucible wherein portionsthereof are of a material such as graphite or heat resisting alloy whichwill heat when subjected to a medium or high frequency electric fieldand this heat is transferred to the briquettes by conduction and/orradiation. The other method is to provide briquettes with a sufficientconductive quality that they in themselves will convert the highfrequency field into heat. In the latter case, the tubular crucible isof a relatively non-conducting type, such as silicon carbide. Anothermethod contemplates a situation wherein the retort is first heated andafter a certain amount of reduction takes place, the briquettes aresufficiently conductive to be further reduced as a direct result of theelectromagnetic energy.

A still further objective of this invention is to provide a binder ofcoal tar pitch which can be pulverized to a fine powder at ambienttemperatures. Although the prior art has used coal tar pitches as abinder reductant, it did not realize the significance of using a typewhich can be pulverized to pass through a fine grade mesh. Such pitches,because of their low content of volatile matter, does not cause swellingupon the heating thereof. In fact, substantial shrinkage of thebriquette occurs during its reduction.

Another important objective of this invention is to provide a briquettewhich can be made of any convenient size for handling by utilizingvertical or slanted tubes in which a great many moving parts areeliminated.

A still further objective of this invention is to provide a systemwherein electric and carbon fuels are economically used for reductionpurposes.

Another important objective of this invention is to utilize medium tohigh-frequency energy from 10,000 to 14,000,000 cycles of inductionelectric power by way of a coil surrounding a refractory retort whichcontains bounded briquettes. The advantage of utilizing this type ofenergy is that briquettes can be converted directly by way of a singlestep from iron ore or other oxides into a liquid iron or steel or othermetals.

A further objective of this invention is to provide means for utilizingan induction powered medium to high frequency water-cooled coilsurrounding a conducting type cylinder such as graphite containing anon-conductive charge, or a non-conductor type such as silicon carbidealundum-zircon, etc. within which a conductive type briquette charge iscontained. When the briquetted ore is of a conducting type such asMagnesite or copper oxide, a nonconductor tube such as silicon carbidemay be used. When the briquetted charge is non-conductive, such aschromite or manganese oxide then the tube will be conductive such asgraphite, to the electric field.

Another object of this present invention is to accomplish the reductionof iron ore withthe aforementioned type briquettes, to the metallicstate with a minimum of capital investment. When the liquid phase isavoided (as by direct reduction of the solid iron ore) it is possible tobuild a plant at lower capital cost.

More specific objects of this invention are as follows:

The provision of a vertical shaft iron ore reduction furnace including ameans for charging the furnace with iron ore mixed with a reducingagent, a means for heating the upper part of the vertical shaft withinduction electricity, a water seal at the bottom of the furnace, and aconveyor to remove the reduced iron, ash, unburned coal and otherreductants, the conveyor comprising at one end a magnetic pulley toseparate the magnetic reduced iron from the ash and other discharge.

The provision of an iron ore reduction furnace including a means forcharging, wherein the reducing agent may be other than coal such as gas,oil, bunker oil, Naptha, charcoal or coke. The liquid reductant may beinjected into the furnace through pipe lines through the wall of thefurnace.

The provision of an iron ore reduction furnace wherein the atmosphere ofthe furnace may be, for all practical purposes, sealed from andexcluding the outside air or atmosphere, thus obtaining a positivecontrol over the inside atmosphere.

An iron ore reduction furnace wherein the upper portion is heated by aninduction electric coil powered by a source of electric power such as 60cycle, medium frequency such as 180 cycle, or higher frequency such as1,000 cycles or higher and where the cold portion of the stack orchamber is insulated from the upper portion and water cooled so that theupper portion can be maintained in the range of about 1,900F. to 2,200F.while the lower portion is cooled by a water sheet and is immersed in awater cooling tank for the purpose of sealing the air from entering thechamber.

The provision of an iron ore reduction furnace where the reduced orecools in the lower portion progressively until it is quenched in a watertank and removed on a conveyor and over a magnetic pulley so it can beseparated by magnetic means from the ash and other products ofcombustion.

In addition, a highly and most significant feature of the presentinvention is the provision of vanes cast integrally with and extendinginwardly from the cylindrical shell around which the induction coil islocated. An important object in transferring the necessary heat into theore being reduced is to transfer the heat uniformly and rapidly acrossthe entire section of the stack so that the reduced ore reaches thereaction temperature as quickly as possible. In general terms, thisobject is accomplished by the electric power from an induction coilheating first a heat resisting alloy or graphite shell and vanes whichextend inwardly therefrom. The large surface area provided by theinterior surface of the cylindrical shell and by the vanes helps totransfer the heat into the charge quickly. Also, as the ore begins toreduce to the metallic form, the electro-magnetic field set up by theinduction coil generates heat directly within the partially reduced ironore as the latter becomes conductive. The overall objective is to obtainas much heat as possible from the reactions between the reductants andthe oxides using a minimum of heat from the inductive electric powerbecause electric power may be more expensive than equivalent exothermicheat obtained from common reductants such as pitch, asphalt, coal andcoke. The heat energy provided by the induction coil, even though it isheld to a minimum to keep the cost down, is absolutely necessary toinitiate and to trigger off the reactions required to reduce the ore.

The provision of a method whereby oxygen or air is injected into thedowncoming charge at a point above the reaction zone or just below thecharging area. This oxygen reacts with the reducing gases or materialsin this area to generate supplementary heat which makes it possible toreduce the consumption of electricity from the induction coil and topreheat the downcoming charge faster so that when it enters the reactionor induction heating zone the ore will reduce more quickly.

The present invention also contemplates a process for the directreduction of ore and the melting thereof in one combined operation and afurnace for carrying out the indicated process. ln the combinationprocess iron ore is reduced directly to metal and then the metal ismelted, both steps being performed in a single furnace and in a combinedoperation, although the individual steps are performed separately. Thus,refined steel is produced by casting the resultant product into billets,ingots or slabs which may then be sold to steel mills where they will berolled into rods, bars, sheets, plates and shapes. This latter form ofraw product, billets, ingots or slabs, will generally command a muchhigher price than synthetic scrap (direct reduced iron) because it isrefined steel ready to roll. This refined metal may also be a high gradepig iron in which the carbon is much higher than steel, for example from3 to 4 percent carbon.

The present invention also relates to a method for direct reduction ofhigh concentrate iron ore or other oxide ores in the form of briquettes(2-12 approx.) or lumps from approx. two inches in size or diameter andunder as it comes from an ore crusher and, in the same furnace or directreduction stack, melting the reduced iron ore so that the product willbe liquid iron or steel which may be cast into ingots, pigs or billets,or may be passed on to another furnace for refining or furtherprocessing. In general, this object is accomplished by the use of avertical or slanted stack in which fine iron ore mixed with acarbonaceous thermosetting reductant binder, such as coal tar pitch orgilsonite or where lump iron ores physically mixed with coal, coke, gas,asphalt, pitch or other reductants, is first heated to reduce the metaland then, in a separate part of the furnace, melted, both heating stepsbeing accomplished by induction electricity. Ores which may be usedinclude iron ore, copper oxide concentrates, chromium ore concentrates,or manganese ore concentrates. Such ore concentrates usually will bebriquettes with five to 12 percent coal tar pitch as a binder reductant,but it also may be handled as loose fine ore or lump ore mixed with areductant such as coke, coal, etc., in the range of 5 to 20 percent byweight.

In contrast with one embodiment of the present invention, there are manypossible applications where it is advantageous to conserve the residualheat in the reduced briquettes and, instead of cooling these reducedmetal briquettes by passing them through a water seal, the presentembodiment contemplates the replacement of the water seal in the lowercooling section of the furnace with an electric induction meltingfurnace similar to the standard types being much used as remeltingfurnaces in industrial areas of the world. Thus, it is possible toexclude the outside air because the bottom of the stack is completelysealed (except for tapping holes in the melting crucible which areclosed when liquid metal is not being removed).

Thus, another object of this species of the invention is to conserve theresidual heat in the reduced briquettes, then melting them while theyare still hot (about l,900 to 2,200F.). ln this way, by combining boththe direct reduction and the melting operation, it is possible to reducethe overall cost of the product.

Further and more specific objects of the present species of theinvention are:

The provision of a method of processing oxide type ores, for example,iron ore, copper ore, manganese ore, and chromium ore, wherein such oresare mixed with a reductant or carbonaceous type thermosetting reductantbinder" such as coal tar pitch or Gilsonite, such materials being of ahard grade high melting point type and charged into a vertical stacksealed from air except at the top, passing the charge down through aninduction heated zone where it is reduced without being cooled, passingthe charge into an induction electric heated melting zone at the bottomof the same furnace where the reduced iron or other metal is melted orrefined, and tapping the liquid metal or draining it from the furnacecrucible to be cast into primary forms such as ingots, billets and pigs.

A method for processing briquettes of finely divided concentrated oxideore mixed and bonded together with powdered high melting point hardgrade coaltar pitch whereby the ingredients are briquetted, and thenpassed through a furnace stack containing a reduction zone operated atabout at about 1,900 to 2,200F. and into a melting zone operated atabout 2,600 to 3,000F. and thence into molds or into other furnaces forfurther refining.

The provision of a method for the direct reduction of iron ore and thesubsequent melting and refining of reduced ore into various alloyswherein a vertical stack is used, the top being open for charging theraw materials and the bottom being closed so that the products ofcombustion of carbon and hydrogen with oxygen in the ore passes out thetop of the stack, it being impossible for air or oxygen to enter thefumace except as desired through injection valves into a preheatingzone, which may be above the reduction zone and just below the chargingzone, where the amount of air or oxygen injected is measured and wherean electric induction melting furnace is located at the bottom, whichfumace may be stationary or non-tilting, and wherein another inductionelectric heating coil is located around the outside of the verticalstack above the melting furnace about midway to the top of the stack,wherein the ore passes through the upper coil after discharge into thetop of the stack where it is heated to about l,900 to 2,200F. to reducethe ore directly without melting, the ore being contained in a heatresisting alloy or graphite lined stack which heats up by induction, andwherein the reduced ore is melted at the bottom by an induction electricmelting coil surrounding a refractory crucible thereby making itpossible to charge raw materials into the top of the stack and draw offliquid refined metal at the bottom. Since the stack is open only at thetop and since below the top the entire stack is an enclosed chamber,including both reducing and melting zones, the entire reduction and themelting operation takes place in the absence of air; the lower part ofthe stack being air-tight and the evolution of hot gases at the toppreventing entry of air into the top of the stack.

The present invention also relates to a method for mixing finely dividediron ore (or other ores) with finely divided reductant materials such aspowdered coal tar pitch, and similar compounds such as Gilsonite andthen compacting such mixtures into dense briquettes up to about 4,000psi after which the briquettes are heated to a comparatively lowtemperature of about 350 to 525F. for thermosetting, caramelizing orhardening after which the briquettes are processed into direct reducediron by passing them through a direct reduction furnace where they areheated for approximately 15 minutes to about four hours at l,900 2,250F.in the absence of air or of oxygen.

A further object of the invention is the provision of a method forproducing a shrunken briquette which is relatively non-porous and inwhich the reduced iron particles are coagulated or welded together intoone dense coherent mass. Contrary to the usual direct reduced spongeiron these dense reduced briquettes do not reoxidize when exposed to theair.

Additional and more specific objects are as follows:

The provision of a method of preparing a briquette or other solid orcompressed form of fine mesh oxide ore such as iron ore concentrate.copper oxide, manganese oxide, chromium oxide, with a fine mesh binderreductant binder such as coal tar pitch, Gilsonite and similar materialsof low volatile matter content by mixing the materials intimatelytogether and then compressing under relatively high pressures thecombined powder into a compact briquette after which the briquette, orsimilar form, is hardened by low temperature baking and then reduced ordeoxidized by passing it through a furnace or in a direct reductionprocess whereby the oxide ore in the briquette is reduced free ofoxygen, the resultant product being a dense chunk of metal or shrunkenbriquette.

The provision of a method for preparing briquettes of fine iron oremixed with fine coal tar pitch, the latter comprising 1 to 15 percent byweight, after which the briquette is heated to about 350F. to about550F. to caramelize or harden the pitch binder so that it may be handledwithout breaking for the purposes of direct reduction of the iron ore tometallic iron.

These and other objects of the invention will become more apparent tothose skilled in the art by reference to the following detaileddescription when viewed in light of the accompanying drawings wherein:

FIG. 1 is a side elevational view in partial crosssection showing theoverall arrangement of a preferred form of the induction heated shaftreduction furnace of this invention;

FIG. 2 is a cross-sectional view in expanded scale of the wallconstruction of the furnace of FIG. 1 showing the joint between upperand lower sections;

FIG. 3 is a side elevational view in partial cross section of a modifiedand improved version of the furnace of this invention showing the systemand means for utilizing the recovery system to preheat briquettes;

FIG. 4 is a side elevational view in partial crosssection of the furnaceof FIG. 3 showing the details of the furnace construction in enlargedscale;

FIG. 5 is a detail in cross-section and in larger scale of the jointbetween a lower cooled section of the furnace and an upper susceptorsection of the furnace;

FIG. 6 is a detail of the joint construction between the susceptorsection of the furnace and the preheat section of the furnace;

FIG. 7 is a detail of the joint between the preheat section of thefumace and the ore input bin of the furnace;

FIG. 8 is a cross-sectional view of the furnace taken in the directionof the arrows as indicated in FIG. 4;

FIG. 9 is a detail of the wall construction of the susceptor section ofthe furnace of FIG. 4;

FlG. 10 is a side elevational view in partial crosssection of a modifiedversion of this invention showing the combination of an inductivelyheated reduction and inductively heated melting furnace.

FlG. ll is partially diagrammatic end view of a direct reduction fumace;

FIG. 12 is a cross-section along the line l2l2 of FIG. 11;

FIG. 13 is a perspective of a briquette for use with the fumace of FIG.1;

FIG. 14 is an embodiment of a reduction system wherein cylindricalretorts are utilized and heating is accomplished by heating the retortsvia electrical energy.

FIG. 15 is a cross-section along the lines l5l5 of FIG. 14 showing aretort construction;

FlG. 15A is a cross-section along the lines of 15-15 of FIG. 14 ofanother embodiment of a retort constructron.

FIG. 16 is a partially diagrammatic, longitudinal cross-section ofanother embodiment of the invention.

FIG. 1 shows an inductively heated shaft furnace comprising a generallyvertical cylinder 20 which further comprises an upper susceptor section22 which preferably is composed of a heat resisting alloy such as 25percent chrome, 20 percent nickel alloy with iron, or any other suitablealloy or heat resistant conductive material such as graphite or siliconcarbide. The wall of susceptor section 22 is preferably one half toabout two inches in thickness. Susceptor section 22 is surrounded by aninsulating cylinder 24 which is preferably composed of A1 0 foaminsulation or insulating brick having a thickness of from 1% to 4 /2inches. A water cooled copper tube 26 is helically wound around theinsulating cylinder 24 to form an induction coil surrounding thesusceptor 22 and separated therefrom by the heat insulating cylinder 24surrounding the susceptor cylinder.

A conductive cylinder 28 is secured below susceptor cylinder 22 and isseparated therefrom by an annular insulating disc 30, which is shown ingreater detail in FIG. 2. The lower conductive cylinder 28 is cooled byan encircling blanket of downwardly flowing water 32 which is providedby an inwardly and downwardly sloping annular member 34 which cooperateswith cylinder 28 to form a water containing trough; the bottom of theannular member being spaced from cylinder 28 to form an annulardischarge port surrounding the conductive cylinder 28.

Since sometimes it is desirable to add gaseous or liquid reducing agentsto the furnace, an input conduit 36 and a control valve 38 are providedfor injecting a reducing fluid, such as a liquid or gaseous hydrocarbon,into the lower portion of the furnace through conductive wall 28. Gasesmay be withdrawn from the upper portion of the furnace, or oxidizinggases injected, through an exit conduit 40 which is controlled by valve42.

Ore is supplied to the fumace by means of a skip hoist 44 whichcomprises a leading bucket 46, which, at its lower end, may rest inexcavation 48 for loading, is carried on a frame 50 by means of cable 52along a track 54 which is curved at the top to discharge the contents ofbucket 46 into surge bin 56. The skip hoist is shown only in ageneralized way since it is conventional and frequently used forcharging blast furnaces and other types of furnaces. Such skip hoists asmay be used with this invention are described by Baumeister, MECHANlCALENGINEERS HANDBOOK, 6th Ed. 1958, McGraw Hill, New York, Chapter Ten,and pages 10 and 13 to 14 in particular. Ore material handling deviceswhich are conventionally used in relation to charging furnaces may beused in this invention. Such devices are described in Zimmer, MECHANI-CAL HANDLING AND STORAGE OF MATERIAL, Crosby, Lockwood & Son, London1922, and more particularly, in the chapter on Fumace Hoists therein.

The loose unbriquetted ore which may be in the form of finely dividedoxides or small lumps, such oxides mixed with finely divided reducingmaterials such as coke or coal in the reduction zone and in the furnace.Thus, a very simple means for controlling the reduction time and overallthroughput of the furnace is provided. While not a necessary feature ofthis invention, it is preferred that one end of the continuous conveyorfor controlling the discharge rate of ore from the cylinder to therebycontrol the furnace throughput and for conveying the reduced ore to aremote point exteriorly of the body of liquid as shown in FIG. 1. Itwill be realized that while a continuous belt conveyor is illustrated asexemplary of the invention, any other continuous conveyor capable ofcontrolling the rate of discharge of the reduced ore from the furnacemay be used.

While this invention is primarily intended for the reduction of iron, itmay be used to reduce other ores such as chrome ore, and manganese orein a manner similar to that used for reducing iron ore.

As illustrated, a preferred embodiment of this invention consists of avertical cylindrical shaft or chamber with a skip hoist commonly usedfor cupolas and blast furnaces. A mixture of iron ore and coal or cokeare charged into the top through a double bell feeder, of the type whichis commonly used to charge blast furnaces. The top portion of the shaftor stack is heated to the reaction temperature by induction electricity.The electric current passes through a spiral watercooled copper tubecoil which surrounds the top half of the furnace and heats up the alloysteel or graphite shell. This metal which operates at high temperatureis a heat resisting alloy such as 25 percent chrome, 20 percent nickel,with the balance mostly iron, or other suitable alloy or refractoryconductive material such as graphite. The shell is a susceptor becauseit is initially heated and in turn it transfers the heat to the charge.This entire operation is based on the fact that when iron ore issubjected to high temperatures about l,900 2,250F. in the presence of acarbonaceous reducing agent such as coal tar pitch or coke in theabsence of free oxygen or air, this ore will be reduced. In oneembodiment, briquettes of ore and reducing agents will be described. Theore passes from surge bin 56 to a weigh-batch hopper 58 and therethrougha double bell valve 60 into the furnace. Such ore charging devices arewell known in the art and are described, for example, in US. Pat. Nos.670,322; 1,865,476; and 2,408,945.

The ore charge passes under the force of gravity, downwardly through thecylindrical furnace sections 22 and 28. The ore is heated to itsreaction temperature by heat conducted from the inner surface ofsusceptor section 22 which, in turn, is inductively heated by currentsinduced from induction coil 26. Electric energy for induction coil 26may be provided by direct connection to an ordinary AC power line ofproper voltage or from any of numerous commercial induction generatorsor static conversion units. Such equipment is described in the tradejournal FOUNDRY of October, 1962, and devices of the type which may beused in this invention to provide the electric energy to the inductioncoil are manufactured and distributed by Inductor Therm Corporation,Rancocas, NJ. As the ore is partially reduced to the metal, the reducedportions of the ore become conductive to the electrical field and maythen be directly inductively heated in the known manner. The reducedmetal, commonly iron, passes downwardly through a cooling zone insidethe cooled conductive section 28. Reduced iron then passes into a bodyof liquid 62 and is carried therefrom by a continuous conveyor 64 whichmay include a magnetic outer pulley 66 to separate the reduced portions68 from the slag, ash, and unreduced portions 70. An important featureof this invention is the ability to control the throughput of thefurnace merely by controlling the speed of the conveyor 64. It will berealized that control of the conveyor also controls the residence timeof the ore at temperature, such as 1,900F. to 2,200F. for from minutesto about four hours in the absence of free air and in the presence ofreducing agents such as coal tar pitch binder carbon, carbon monoxide,and hydrogen, the oxygen will leave the ore and combine with a reducingagent. A sample of this type of reaction is:

F6203 T CO2 2P6 Among the outstanding points of the invention are thefollowing:

A closed chamber with an iron ore and reductant charge is heated by aninduced electrical field. This is the only known practical means forheating a closed chamber. If it were heated by the usual means, asdescribed in the prior art, it would be necessary to have an opening inthe furnace and the furnace would no longer be sealed from the outsideair. In addition, in the present process only one stack is required. Theonly refractory is a coating of from 1 k to 4 /z inches of alumina (M 0insulator on the outside of the upper portion of the stack between theinductor coil and the stack or susceptor which is a conductor as alloysteel or graphite. Of course, alumina bricks may be used.

The heat loss is small because the hot portion is covered with aninsulator. The lower portion is insulated by a separating heat andelectrical insulator annulus from the upper half. This pennits the lowerhalf to be 'cooled by a flowing sheet of water which is drained off intoa body of water in a water tank at the bottom and which may berecirculated through a cooler and repassed over the lower portion of thestack.

FIGS. 3 and 4 illustrate another embodiment of the present invention.Generally, the furnace 120 of this embodiment is similar to furnace aspreviously described, and comprises an upper susceptor section 122 whichis surrounded by an insulating cylinder portion 124 around which helicalwater cooled copper coils 126 are wound to fon'n an inductiJn coil. Alower cooled conductive section 128 is secured to susceptor section 122and separated therefrorr by an annular insulating disc 130. Anencircling blanket of downwardly flowing water 132 is supplied fromannular member 134 which cooperates with conductive section 128 to forma trough, similar to the manner previously described with respect tofurnace 20. Means for injecting a reducing fluid into the lower portionof the furnace 136 comprises, in furnace 120, a manifold communicatingat a plurality of points with the inside of cooling cylinder 128. Ametering pump 138 may be provided to control the inflow of reducingliquids or gases through manifold 136 to the furnace 120. A plurality ofconduits 140 extend through the susceptor section 122 and open in a zoneabove the induction coil for injecting oxidizing gas into the furnace ata point above the reducing zone therein for reacting with reducingmaterials to preheat the ore in the top portion of the furnace.

A skip hoist 144 having a bucket 146 which, in its lowered position mayrest in depression 148 and which is guided by frame 150 and lifted bycable 152 along guide track 154 where the ore is discharged into a surgebin 156. After reduction, the ore is discharged into a body of water 162and carried therefrom by a conveyor 164 which may include a magneticseparator 166, in the manner described with respect to the furnace 20.The ore is then dumped into a container 172 where it may be transferredto a melting furnace, sampled, or otherwise handled or stored.

Significant differences exist between the furnace 120 and furnace 20 asdescribed previously. The connection between susceptor section 122 andconductive section 128, which is shown in enlarged detail in FIG. 5, andwhich may include a bolt 131, is generally similar to the connection ofthe susceptor 22 and conductive section 28; however, an additionalpreheat section is connected, by means shown in enlarged detail in FIG.6, to the top of susceptor section 122. The preheat section may comprisea preheat cylinder 174 surrounded by an insulating cylinder 176 which isconnected by a bolt, or other fastening means, directly to susceptorsection 122. The surge bin 156, which in the present embodiment issurrounded by insulating member 180, is connected by a bolt 182, orother convenient fastening means, to the top of heater section 174, asshown in greater detail in FIG. 7.

FIG. 8 shows in cross-section the internal constructional features ofsusceptor 122. It will be seen that a plurality of vanes 184 and 186 aresecured to the inner surface of the susceptor cylinder 122. The vanesextend radially inwardly to the reduction zone in the susceptorcylinder. In a preferred embodiment, susceptor section 122 may be builtup of a plurality of cylinder segments 188 which may be secured to eachother by a weld bead 190, as best shown in FIG. 9.

Referring again to FIG. 3, the furnace of this embodiment may comprise amixer and feed bin 192 for iron or other oxide ore plus binder or otherreductant. The mixed ore and reductant are fed to a briquette machine194 and are conveyed through a heating zone 196 by a conveyor 198 whichmay be of any conventional type. Heat is supplied from an enclosure 200which is secured to the top of the vertical cylindrical furnace forcollecting the gases expelled therefrom and passing them through conduit202 to the heating zone 196. The heated gases may be propelled by a gaspump 204, in conduit 202, which may be of any convenient type. Thus theheat from the furnace is recovered and used to preheat briquettes whichhave been formed by briquette machine 194. The preferred temperature inheating zone 196 is in the range of 350 to 550F., preferably about 525F.It may be necessary or desirable to supplement the heat from the furnacefor regulation purposes. Supplemental heat may be provided by anyconvenient means, such as an electrical resistance heater or a gas firedheater adjacent the heating zone 196.

The hard caramelized briquettes, which may be of the type describedhereinafter, are carried by skip hoist 144 to the top of the furnace. Asthese briquettes pass downwardly through the furnace they may bepreheated by the injection of air or oxidizing gas into conduits 140,which are located above the reduction zone. The oxidizing gas reactswith part of the reducing material associated with the briquettes topreheat the briquettes to a point just below their reductiontemperature. As they pass downwardly through the furnace, the heatedbriquettes contact vanes 184 and 186 which efficiently transfer heat tothe briquettes. Vanes 184 and 186 induce current and heat flow radiallyinwardly from the susceptor section 122. It will be understood, ofcourse, that the vanes are composed of a high temperature resistantsusceptor material. In this manner the briquettes are preheatedeconomically by using abundant carbonaceous fuel and the precisetemperature required for most efi'icient reduction is controlled byinduction heating. This combination of preheating and induction heatingis highly desirable for high efficiency. A spacer support 206 of anynon-conductive material may be used to position coil 126.

The embodiment of the furnace as described is particularly advantageousin that it permits a continuous process including the interrnixing ofore and reducing agent, the formation of briquettes from theintermixture of ore and reducing agent, preheating the green briquettesto harden, or caramelize them to permit handling, and the reduction ofthese briquettes, after preheating, by carefully controlled inductiveheating.

In order to further increase the efiiciency of the reduction furnace,vanes have been provided which are, in a preferred embodiment, integralwith and extending inwardly from a cylindrical shell around which theinduction coil is located. In this manner, heat is transferredefficiently to the ore being reduced, and is transferred unifonnly andrapidly across the entire section of the stack so that the reduced orereaches the reaction temperature quickly. The large surface areaprovided by the interior surface of the cylindrical shell, and increasedby the inwardly extending vanes, helps to transfer the heat into thecharge quickly. In addition, as the ore begins to be reduced to themetallic form, the electro-magnetic field set up by the induction coilgenerates heat directly within the partially reduced iron ore as thelatter becomes conductive.

While the furnace has been shown in a generally vertical plane; it willbe realized that it is necessary only that the fumace be orientedupwardly from the horizontal to permit gravity feed through the furnace,or, if the furnace is horizontally oriented, to provide means forconveying the ore through the fumace. It will also be noted that in theembodiment of the furnace just described, furnace 122, the top of thefurnace is partially open to the atmosphere. While it is generallydesirable to maintain the to of the fumace stack closed to prevent lossof heat and valuable reducing gases, it will be understood that thefurnace may be operated with an open top, the flow of exiting reducinggases preventing entry of oxidizing gases into the furnace.

The temperature of the furnace may be precisely controlled by the use ofinduction heating, and the reducing atmosphere in the fumace iscontrolled by the amount of reducing agent intermixed with the ore andis further controlled very precisely by the selective addition ofreducing liquids or gases by injecting means 136. Of course, by carefulpreparation of the ore intermixture with reductant, it is not necessaryto supplement the reducing material. The temperature of the briquettesas they enter the reducing zone may be carefully controlled by varyingthe amount of oxidizing gas which is injected into conduits 140.

While an experienced operator can make the necessary adjustments inthroughput by varying the speed of conveyor 164, in oxidizing orreducing conditions by varying the input of reducing or oxidizingmaterials through injecting means 136 and 140 and in the temperature ofthe ore in the furnace by controlling the power input to induction coil126 by merely observing the color of the exiting flame, it will berealized that the control process may be also automated as a function ofthe exhaust gas which may be extracted or sampled through an outputconduit 208. Thus an automatic sampler and control system, such as thosebuilt and designed by Minneapolis-Honeywell and by Leeds and Northropmay be used to automatically control the furnace.

In a specific embodiment, the susceptor section 122 may be a 29% incho.d. cylinder having a wall thickness of one inch and having vanes 184extending inwardly to the circumference of a 13% inch circle and vanes186 extending inwardly to the circumference of a six inch circle. Thesusceptor cylinder 122 may be made of nickel chrome alloy or otherrefractory type conductor such as graphite and may be eight feet long.The preheating zone may be of the same diameter, without vanes, and maybe two feet long, below a three foot long surge bin. The cooledconductive cylinder may be of the same diameter and 10 feet in length.Conduits 140 are conveniently /2 inch diameter pipes and may be composedof a heat resistant alloy. FIGS. 3 and 4 are shown generally to scalewith respect to the above dimensions and it is believed that one skilledin the art of furnace design and construction would have no difficultyin carrying out the invention.

FIG. 10 discloses a combination reduction and melting furnace whichprovides means for utilizing the heat generated during and prior to thereduction step. This furnace may be of the type described with referenceto furnace 20 or may be of the improved type described with reference tofurnace and comprises a top part 301 where the ore is preheated, amiddle part 302 for induction electric heating coils 303, either shellor susceptor 304, which is made of heat resistant alloy, and a lowerpart 305 which consists of an induction electric melting furnace linedon the inside with refractory material 306.

The ore is charged in at the top by skip hoist 307, or by other means,and the stack is maintained completely full of charge ore and reductantat all times while in operation. In the embodiment shown, the top isusually open but it may be partially closed to exclude outside air. Atapping spout 308 at the bottom of the lower section of the meltingfurnace is used to empty the furnace of liquid metal. There is also arelatively vertically lo cated tapping spout 309 located at a higherlevel to remove slag which accumulates on top of the liquid bath.

While the furnace of FIG. has been described in rather general terms, itwill be understood that the same constructional features and equipmentwhich have been described hereinbefore and which are used in the priorart may be utilized in this combination furnace.

In the embodiments of the furnace previously described, reduced iron orother metal briquettes for sale as synthetic scrap and for melting inthe usual melting furnaces, such as direct are or open hearth, LDoxygen, induction or other furnaces, to primary forms of steel or ironsuch as ingots, billets or pigs have been described. in the presentinvention, however, has been found advantageous to conserve the residualheat in the reduced briquettes and, instead of cooling these briquettes,to pass them directly into an induction electric melting furnace similarto the standard types used as remelting fumaces.

For the relatively small amount of induction heat required both in thereduction section and in the melting section it is convenient to use a60 cycle current from the usual standard type power source, such as adistribution transformer, or other frequencies such as 180 cycles from astationary frequency changing transformer or 1,000 cycles from a highfrequency generator.

In using briquettes bonded with pitch, as will be described more fullyhereinafter, the mixture of fine ore and pitch would first be briquettedand then hardened by heating at about 350 to 525F., then charged in thetop of the furnace, which is kept filled. As the liquid metal is tappedfrom the induction electric crucible which forms the bottom of thestack, the charge descends by gravity in the stack thus continuallyfeeding the reduced briquettes into the molten bath from which themolten metal is tapped off for further processing. In using loose lumpor fine iron ore, not briquetted, the same operation is followed exceptthe lump or fine ore is not bonded with the pitch but instead is mixedby mechanical means with reductant such as coal, coke or charcoal andthen charged into the top of the stack.

The outstanding points of the invention may be enumerated as follows:

Direct reduction and melting in the same production unit is combined.

The advantages of mixing fine hard pitch with fine high grade ore, inbriquettes as described hereinafter, thus obtaining an acceleratedreaction by utilizing maximum surface contact area between ore andreductant and then melting the reduced ore without letting it first cooldown is obtained with the resulting efficiency therefrom.

The product, a refined metal ingot or billet, free of excess slag oroxide, is suitable for rolling directly to the final product, or if itis in the form of pig metal, is suitable for sale directly as asynthetic steel scrap or pig iron.

While other direct reduction processes for iron ore give a product whichis light or of low density and does not easily melt and which usuallyhas about 10% of oxide and slag material, such as Si0 and A1 0 by thepresent apparatus and process these impurities are floated off as slag,and a refined metal product wherein the iron content is about 98 to 99.9percent iron or metal is produced.

The electric power required to melt the red hot reduced briquettes ismuch less, about one-half, than is required to melt cold scrap or metalbriquettes.

The present process does not require huge plants in the usual sense,such as hundreds or thousands of tons per day which require huge capitaloutlays. Plants of the type described can be economical in any size froma few tons, such as ten tons, up to hundreds or thousands of tons perday. One small stack can make ten tons per day, a large stack can make50 tons per day and, for increase in size over 50 tons, multiple stacksmay be used. For example, ten stacks may be used to make 500 tons perday.

By using the method reducing iron ore and melting the resultant productall in a single combustion furnace unit in a highly reducing atmosphere,there is less oxidation and therefore all the metal in the ore isrecovered, whereas in other usual steel making processes such as theopen hearth, LD oxygen, electric arc, or in any other melting furnaceswhere the molten bath is exposed to the oxygen of the air, there isconsiderable loss of the metal due to oxidation.

By the present method and apparatus it is possible to produce manydifferent kinds of iron or steel, high carbon, low carbon, alloy steeland alloy cast irons. This is made possible and is subject to very closecontrol because, first, a highly reducing atmosphere not only in thereduction zone but in the melting zone is utilized, and secondly, thefinal analysis of the alloy is determined and controlled to the desiredcomposition by varying the composition of the charge going into thefurnace. For example, if a chrome alloy is desired, chromium,ferrochrome or chrome ore may be added to the charge. In this manner, itis possible to make stainless steel, for example 18-8 or similaranalysis, by using a charge made up of chrome ore, nickel and iron ores.

While the furnaces hereinbefore described are highly versatile and maybe used with a large variety of ore and reductant combinations and oresin a large variety of forms, a particularly advantageous and preferredprocess has been developed and is carried out utilizing the furnaces ofthe present invention. Generally, this invention consists of taking afinely divided ore concentrate and mixing it with a finely dividedcarbonaceous reductant binder, preferably powdered coal tar pitch. Themixing takes place in the dry state, using an ordinary paddle orconcrete bath type mixer whereby the mixing machine, by rotation or bymechanical agitation, obtains a thorough, intimate and uniform mixturethroughout. The combined materials are then pressed into hard compactbriquettes on an ordinary molding or briquetting machine. At this stagethe green briquettes must be handled with care. They are put through awarm oven of about 350 to 525F. where the pitch is caramelized(hardened) and the briquette becomes hard and tough and may safely behandled by conventional means. The briquette may then be dipped orimmersed in liquid asphalt, or otherwise coated with liquid asphalt,and, as it is extracted from the asphalt, powdered coal or coke isdusted onto the sticky asphalt in a manner similar to stuccoing of afinely divided hard material on a fresh plaster wall. This briquette isthen ready to charge into the direct reduction furnace so that the oremay be converted directly with or without melting, into metals such asiron, copper, chromium, manganese or other metals.

In carrying out the process, the fine ore is mixed with a finely dividedcarbonaceous thermosetting reductant binder such as coal tar pitch orGilsonite. When finely divided iron ore, for example 325 mesh, is mixedwith finely divided coal tar pitch of about the same mesh, using about 1to 15 percent pitch, and the balance, the finely divided andconcentrated iron ore (by weight) and the mixture is formed by pressureinto briquettes of about two inches to about 12 inches in diameter byabout two inches to eight inches in height and the briquettes are heatedto approx 350 to 525F. to thermoset or caramelize the pitch, thebriquettes are hard and tough and may be handled without breaking.

When these hard, tough briquettes are heated in a highly reducingatmosphere to approximately 1,900 to 2,200F. the oxygen of the ore isremoved by the pitch, which is a combination reductant-binder, and aniron briquette in shrunken form consisting of relatively solid metaliron with a slight amount of gangue material, such as silica andalumina, is produced. Quite unexpectedly, this shrunken briquette, aboutone half the former volume, is different from the usual sponge iron inthat it is relatively non-porous. As the oxygen was re moved, theremaining reduced iron particles coagulate or weld together into onedense coherent mass. This is distinctly more valuable and useful thanthe usual porous low density form of sponge iron produced with thebinder reductants of the prior art. The product herein does not havecharacteristics of ordinary sponge iron because it is highly dense.Thus, it will not soak up wa' ter, is not easily reoxidized in the air,and when fed into a molten bath it sinks readily and is easily meltedwhereas the usual low density sponge iron or reduced iron pellets lie onthe surface of a molten bath of iron or steel, reoxidize and do notreadily melt in.

In its most comprehensive form, the process of this inventioncontemplates the machining or hot forming by forging, of the solid,dense, shrunken metal bri quettes into useful articles, such as nuts andbolts.

While coal tar pitch is a highly preferred material, other materials maybe used as a partial replacement for pitch, for example, powdered cokeand gilsonite (a natural form of pitch). A combination of pitch withthese materials may be used, such as five percent powdered pitch, fivepercent powdered coke, and five percent fine powdered coal or asphalt.

Binder materials used to make pelletized iron ore are usually clays,such as bentonite, or water glass. These are expensive and areultimately wasted since they have no reducing power. On the other hand,my invention provides for materials like coal tar pitch which serve bothas binder and as reductant and thus have dual or double function andavoid the waste inherent in the use of bentonite and similarnon-reductive binders. In addition, these non-reductive binders increasethe nonmetallic gangue content.

A pitch of the type which has been found satisfactory was obtained fromthe J. S. McCormick Co. of Pittsburgh, Pa., and has an approximateanalysis as follows:

Melting point 300 to 320F.

Carbon 93.7%

Sulfur 0.5%

Hydrogen 4.1%

Nitrogen 1% Oxygen 0.6%

Ash 0.1%

The melting point must be sufficiently high so that the block pitch willbe ground to a fine mesh at ambient temperatures without gumming" andalso so it will mix dry with the fine ore concentrate. Iron oreconcentrates with at least percent iron, and preferably from to aboutpercent iron, are most advantageously used in the present process.Briquettes composed of such iron ore and pitch, bonded in the mannerdescribed in the process as reduced, do not tend to sinter or hang up inthe furnace as has been a problem heretofore. There is no problem at allwith bridging in the reducing or melting furnace with the briquettes ofthis process, especially briquettes which have been dipped in asphaltand stuccoed with powdered coal or coke. These desirable results occurin part from shrinkage of the briquettes during reduction.

The invention additionally encompasses the use of coal tar pitch-orebriquettes in novel crucible tubes heated by conventional fuels as wellas by medium to high frequency inductive electric energy. Referring nowto FIG. 11, the numeral 410 indicates furnaces of a different type whichcan be used in the invention. The furnace 410 is comprised of an outerwall 412 of a refractory material. Such furnaces can be electricallyheated or can utilize conventional fuel such as gas, oil, coke or coalas is well known in the art. In the FIG. 11 embodiment, the fuel or heatis charged into the furnace by way of a conventional means, forinstance, such as a gas line from burner 414. The furnace has thecapacity to reach operating temperatures in the range of 2,350F. Athermocouple 416 is utilized as a sensor and control mechanism. Thefurnace is equipped with a vent 418 to allow the gases of combustion toescape.

The end walls 420 and 422 of the furnace are also of a refractorymaterial. Disposed within the furnace are a plurality of crucible tubes424. These tubes are normally comprised of sections which are sealedtogether with a refractory at joints 425. The tubes are placed at aslant of approximately 25 to 40 and extend from an upper feed opening427 in the wall 422 to a lower discharge opening 426 in wall 420. In theend elevation of FIG. 1 1, it can be seen that a pair of furnaces of the410 type can be disposed with their walls 422 in spaced opposingrelation on either side of a platform 427. At its upper end, retort 424is enclosed by a door 428 and at its lower end a door 430. Supports 432support the tubes in their sloping positions. The tubes are adapted tobe charged by briquettes of a type indicated by the numeral 436. Thebriquettes can be brought to the loading area of platform 437 by way ofthe chute assembly 439. Sets of perhapd twenty retorts, ten on eitherside of the platform, can quite efficiently be fed from a single chute.The chute can be loaded at the end of the platform and, whilehorizontal, moved to a position over a retort.

A cross section of tube 424 is shown in FIG. 12. The dimensions of thetube and the dimensions of briquetted charges 436 are dependent on thepractical consideration of easy handling. The briquettes 436 are formedwith a plurality of holes 440 for gases to egress during reduction.

The inner lower surface of retort 424 is lined with graphite layer 438.The graphite layer supports the charges 436 and presents a surface oflesser friction than a refractory material such as silicon carbide.

In operation, a charge of briquettes is loaded into chute 431 andbrought to a position adjacent a retort to be filled. Door 428 is openedand door 430 is closed. By a simple tilting manipulation of the hoistmeans 431, the chute is loaded into the retort. Door 428 is then closed.The charge is then subjected to heat from burner 414. The retort 424 canbe of a material such as graphite or of a material such as siliconcarbide. There are advantages to a retort having an inner liner ofgraphite and an outer layer of silicon carbide. The graphite isresistant to the abrasions of the briquettes and to the conditionswithin crucible. The silicon carbide, on the other hand, resists thehigh temperatures and other abrasive conditions in the furnace itself.

Another embodiment of a furnace is shown in FIG. 14. In this embodiment,a crucible or retort 446 is surrounded by a water-cooled induction coil447 capable of operating at from 4,000 to 14,000,000 cycles per second.This invention encompasses two different methods of utilizing thisstructure. One uses a conductive refractory tube such as graphite with arelatively non-conductive briquette charge and the second uses aconductive charge with a relatively non-conductive refractory tube suchas silica carbide. The crucible tube 446 can be vertical or slanted andis made of a combined silicon carbide graphite material.

In FIGS. 14 and 15 there is shown an embodiment wherein heat is suppliedto the charge via coils 447 about the retort. The coils extend thelength of the retort 446. In this embodiment the retort is manufacturedof an inner liner of graphite 449 and an outer layer of non-conductingmaterial such as a refractory 448. As in the FIG. 1 1 embodiment, thetube is heated and the charges are reduced via conduction and radiationfrom the retort.

A variation of the retort is shown in FIG. 15a. Here there is an innerlayer 450 of silicon carbide, a graphite layer 449 and an outerinsulating layer 447 of a refractory material. The coils 447 are aboutthe layer 448. This variation is used with a frequency generator 458means capable of producing frequencies of a level capable of inducingheat in the briquettes themselves. The briquettes become increasingconductive as they begin to reduce and this reduction will accelerate asa result.

in FIG. 16 there is shown a vertical refractory retort 460 which canreceive a disoriented charge of briquettes. At its lower end, the retortis formed with a restriction orifice 462 substantially less in size thanany single briquette. A coil assembly 464 adapted to emit ultra highfrequencies from 4K to 4.5 megacycles, surrounds the refractory retort460. With such a frequency source, heat of sufficient intensity firstreduces and then melts the ore. As the metal liquifies, it flows throughthe orifice 462 to a holding melting fumace 465 for further processing.Coils 466 of more conventional induction frequencies maintain the liquidmetal at desired temperatures.

In a general manner, while there has been disclosed an effective andefiicient embodiment of the invention, it should be well understood thatthe invention is not limited to such embodiment as there might bechanges made in the arrangement, disposition, and form of the partswithout departing from the principle of the pres- *ent invention ascomprehended within the scope of the accompanying claims.

I claim:

1. A process for producing molten metal for casting purposes comprisingthe steps of,

forming a mixture of finely divided metal ore concentrate with a coalbase pitch,

compressing said mixture into soft briquettes ranging in size from 2 to12 inches in diameter and 2 to 8 inches in height,

thermosetting said soft briquettes to form hard briquettes at atemperature ranging from approximately 350F. to 550F.

continuously passing a multiplicity of said hard briquettes downwardlyunder the force of gravity through an elongated reducing zone,

excluding substantially all oxygen from said reducing zone,

reducing said hard briquettes in said reducing zone by heating said hardbriquettes to a temperature ranging from approximately 1,900F. toapproximately 2,200F. so that a relatively non-porous, shrunkenbriquette is formed that is substantially reduced, and

passing the briquettes from the reducing zone into a melting zone toproduce a supply of molten metal, thereby conserving the residual heatin the briquettes from the reducing zone.

2. The process of claim 1 wherein said mixture comprises approximately 1to 15 percent coal base pitch and to 99 percent finely divided metal oreconcentrate by weight.

3. The process of claim 1 wherein said briquettes are reduced in saidreducing zone by at least percent.

4. The process of claim 1 further including the step of injecting afluid carbonaceous material onto the briquettes below the reducing zonewhile the briquettes retain residual heat from the heating step.

5. The process of claim 1 further comprising the steps of continuouslypassing a multiplicity of hard briquettes through a preheating zoneprior to passing said briquettes through the reducing zone,

conducting gases produced in the reducing zone into the pre-heatingzone,

introducing oxygen into the pre-heating zone for reaction with the gasesfrom the reducing zone to utilize the residual and chemical energy inthe gases from the reducing zone to pre-heat such hard briquettes, and

continuously passing such multiplicity of hard, preheated briquettesdownwardly under force of gravity into the reducing zone.

6. The process of claim 5 wherein heating the briquettes during passagethrough the reducing zone comprises encircling the reduction zone with asusceptor material, and

inductively producing current flow in the susceptor material toresistively heat the susceptor material. 7. The process of claim 6further comprising the steps of conducting the induced current flowradially inward into the reduction zone at a plurality of points; and

conducting the heat from the encircling susceptor material radiallyinward into the reduction zone at a plurality of points.

8. The process of claim 1 wherein heating the briquettes during passagethrough the reduction zone comprises the steps of encircling thereduction zone with a susceptor material, and

19 i 20 inductively producing current flow in the susceptor into.thereduction zone at a plurality of points; and material to resistivelyheat the susceptor material. conducting the heat from the encirclingsusceptor 9. The process of claim 8 further comprising the stepsmaterial radially inward into the reduction zone at of a plurality ofpoints.

conducting the induced current flow radially inward 5

1. A PROCESS FOR PRODUCING MOLTEN METAL FOR CASTING PURPOSES COMPRISINGTHE STEPS OF, FORMING A MIXTURE OF FINELY DIVIDED METAL ORE CONCENTRATEWITH A COAL BASE PITCH, COMPRESSING SAID MIXTURE INTO SOFT BRIQUETTESRANGING IN SIZE FROM 2 TO 12 INCHES IN DIAMETER AND 2 TO 8 INCHES INHEIGHT, THERMOSETTING SAID SOFT BRIQUETTES TO FORM HARD BRIQUETTES AT ATEMPERATURE RANGING FROM APPROXIMATELY 350*F, TO 550*F. CONTINUOUSLYPASSING A MULTIPLICITY OF SAID HARD BRIQUETTES DOWNWARDLY UNDER THEFORCE OF GRAVITY THROUGH AN ELONGATED REDUCING ZONE, EXCLUDINGSUBSTANTIALLY ALL OXYGEN FROM SAID REDUCING ZONE, REDUCING SAID HARDBRIQUETTES IN SAID REDUCING ZONE BY HEATING SAID HARD BRIQUETTES TO ATEMPERATURE RANGING FROM APPROXIMATELY 1,900*F. TO APPROXIMATELY2,200*F. SO THAT A RELATIVELY NON-POROUS, SHRUNKEN BRIQUETTE IS FORMEDTHAT IS SUBSTANTIALLY REDUCED, AND PASSING THE BRIQUETTES FROM THEREDUCING ZONE INTO A MELTING ZONE TO PRODUCE A SUPPLY OF MOLTEN METAL,THEREBY CONSERVING THE RESIDUAL HEAT IN THE BRIQUETTES FROM THE REDUCINGZONE.
 2. The process of claim 1 wherein said mixture comprisesapproximately 1 to 15 percent coal base pitch and 85 to 99 percentfinely divided metal ore concentrate by weight.
 3. The process of claim1 wherein said briquettes are reduced in said reducing zone by at least90 percent.
 4. The process of claim 1 further including the step ofinjecting a fluid carbonaceous material onto the briquettes below thereducing zone while the briquettes retain residual heat from the heatingstep.
 5. The process of claim 1 further comprising the steps ofcontinuously passing a multiplicity of hard briquettes through apreheating zone prior to passing said briquettes through the reducingzone, conducting gases produced in the reducing zone into thepre-heating zone, introducing oxygen into the pre-heating zone forreaction with the gases from the reducing zone to utilize the residualand chemical energy in the gases from the reducing zone to pre-heat suchhard briquettes, and continuously passing such multiplicity of hard,pre-heated briquettes downwardly under force of gravity into thereducing zone.
 6. The process of claim 5 wherein heating the briquettesduring passage through the reducing zone comprises encircling thereduction zone with a susceptor material, and inductively producingcurrent flow in the susceptor material to resistively heat the susceptormaterial.
 7. The process of claim 6 further comprising the steps ofconducting the induced current flow radially inward into the reductionzone at a plurality of points; and conducting the heat from theencircling susceptor material radially inward into the reduction zone ata plurality of points.
 8. The process of claim 1 wherein heating thebriquettes during passage through the reduction zone comprises the stepsof encircling the reduction zone with a susceptor material, andinductively producing current flow in the susceptor material toresistively heat the susceptor material.
 9. THe process of claim 8further comprising the steps of conducting the induced current flowradially inward into the reduction zone at a plurality of points; andconducting the heat from the encircling susceptor material radiallyinward into the reduction zone at a plurality of points.